Fluxes

ABSTRACT

A solid solution of 28 to 32% MnO, 30 to 35% FeO, 25 to 30% CaO and 8 to 12% MgO is advantageously used as a flux, together with external lime, in the refining of steel. As an adjunct, a solid solution of 80% CaO, 15% MnO and 5% FeO is used as a flux without any or with only a minimum of external lime.

United stateS Patent 1 1 [111 3,884,678

lyengar May 20, 1975 54] FLUXES 3,311,465 3/1967 Ban 75/5 3,669,6186/1972 Coppel 75/94 [751 Inventor: Ramachandra lyenga's 3,726,665 4/1973Minnick 75/94 Lebanon, 3,793,006 2/1974 Kewawa 75/94 Assigneez Jones &Laughlin Steel C p Rmesch Pittsburgh, Pa.

Primary Examiner-P. D. Rosenberg [22] Filed: Feb. 4, 1974 Attorney,Agent, or Firm-T. A. Zalenski [21] Appl. No.: 439,465

[57] ABSTRACT [52] U.S. Cl 75/52; 75/94 A solid solution of 28 to 32% 30o 5% 51 1m. (:1 CZIC 7/00; @215 9/10 to Q10 and 8 to 12% 3 isadvantageously [58] Field of Search /52, 53, 94, 5 used as a fl togetherwith external lime, in the r fining of steel. As an adjunct, a solidsolution of [56] References Cit d C20, 15% MnO and 5% FeO is used as aflux without any 01' only a minimum Of external 3,259,486 7/1966 Kootz75/52 6 Claims, No Drawings .of pneumatic steelmaking processes, such asFLUXES This invention relates generally to fluxes and particularly tofluxes useful in the refining of steel by means the basic oxygen furnace(BOP) process. 1 e

In the refining of molten iron into steel, fluxes are added to the meltprimarily for the purpose of reacting with oxidizable impurities in themolten iron to form a slag having the chemical and physical propertiesnecessary for refining the iron to steel in an efficient manner.Sufficient calcium oxide, in the form of lime primarily, is added to themelt to establish a calcium oxide to silicon oxide ratio of at leastapproximately three to one in order to promote sulfur removal from themolten iron. The silicon oxide is formed, of course, by the oxidation ofthe silicon in the molten iron. Iron oxide which is both added to themelt and is formed as a result of oxidation of the iron in the melt alsoacts to flux the lime.

Magnesium oxide is added to create a slag which is essentially saturatedin that compound and, thus, minimize the extraction of magnesium fromthe refining vessel refractory lining, thereby extending refractorylife.

Manganese oxide acts to put lime into solution and to provide thecorrect fluidity to the slag. This is particularly significant in theBOP process where the proper fluidity is important in minimizingslopping (the ejection of slag from the refining vessel) and the buildup of slag on the oxygen lance.

The use of the individual compounds discussed above as slag-formingmaterials is not new with me. What is new, however, is theirintroduction into the melt in solid solution. Thus, according to a firstembodiment of my invention, a solid solution of 28 to 32% MnO, 30 to 35%FeO, 25 to 30% CaO and 8 to 12% MgO together with external lime areadded as the fluxing materials to a pneumatic steel-refining vessel,such as a BOF. In a second embodiment of my invention, an alternatefluxing material consisting of a solid solution of 80% CaO, 15% MnO and5% FeO is used with little or no external lime.

Since each of the above-mentioned compounds must first go into solutionbefore they can perform their slag functions, I reduce the time of therefining period, i.e., the blowing time in a BOF operation, by addingthe compounds in solid solution form. The net effect of adding thecompounds in this manner is to create a fluid and reactive slag in ashorter time than is otherwise the case because less thermal andchemical energy is required to develop the proper slag properties.

A better understanding and appreciation of my invention will be had fromthe following detailed description of the embodiments of the inventionas applied to a BOF process.

In the first embodiment of my invention, I take 28 to 32% MnO, 30 to 35%FeO, 25 to 30% CaO and 8 to 12% MgO and form a solid solution of thesecompounds. By a solid solution, I mean a material where the atomicstructure of the manganese, iron, calcium and magnesium is arranged insome coordination with oxygen. The solid solution may be analogized to asteel alloy and is to be clearly distinguished from a mixture of thecompounds in which each compound maintains its separate integrity.Preferably, the solid solution consists of 28% MnO, 35% FeO, 25% CaO and12% MgO.

heating of the mixture to create the solid solution can be effected invarious ways. When used in conjunction with the BOF process, the mixturecan be heated during the period the BOP vessel is preheated, ifpreheating is used. Alternatively, the vessel may have Sufficientretained heat from a melt which has just been tapped that the mixtureneed only be injected into the empty vessel and held there for a shorttime to create the solid solution. Thereafter, the molten iron for thenext refining cycle is introduced into the vessel. Additional proceduresfor heating the mixture to form a solid solution include using waste gasheat from any of the processes producing such heat around a steel plantand external heat sources such as furnaces or kilns.

In a typical BOF steelmaking operation, lime, dolomitic line andfluorspar are used as the fluxing agents. The lime represents theprimary slag-forming ingredient. The dolomitic lime acts primarily topreserve lining life and the fluorspar is added to speed-up thedissolution of the lime.

According to my invention the solid solution of MnO, FeO, CaO and MgO isadded to the hot metal .in place of the dolomitic lime and fluorspar.However, external lime, that is, lime in addition to that contained inthesolid solution is added in conventional quantities less approximatelythat amount of lime contained in the solid solution. The solid solutionflux of my invention reacts rapidly with the silica in the slag toproduce a reactive slag in which external lime solution takes place morequickly than through the use of fluorspar; and, of course, in a BOFoperation where refining cycle times are measured in terms of minutes,the reduction of the refining cycle even by a few minutes is ofsignificance.

The rapidity with which the solid solution flux of my invention reactsis a result, primarily, of two circumstances: First, because the flux isalready in solid solution when added to the molten iron, no energy isrequired to create a solution of the materials which make up the flux,and the only chemical and thermal energy required is that needed to meltthe flux; Second, there is a catalytic effect in the sense that areactive slag is created at an absolute energy level lower than thatwhich would otherwise be required. In otherwords, if an absolute energylevel of x is required to create a reactive slag in a conventionaloperation, an absolute energy level of less than x will produce areactive slag using the solid solution of my invention.

In the second embodiment of my invention, I provide a flux in whichessentially all the lime required is put into solid solution with otherfluxing materials and little if any external lime is used. This fluxconsists of a solid solution of CaO, 15% MnO and 5% FeO. Dolomitic limecan be added externally of the solid solution to extend refractory life.

I claim:

1. A solid solution of flux consisting essentially of 28 to 32% MnO, 30to 35% FeO, 25 to 30% C210 and 8 to 12% MgO.

2. A solid solution flux encompassed by claim 1 and consistingessentially of 28% MnO, 35% FeO, 25% CaO and 12% MgO.

3. In a pneumatic process for refining iron into steel where lime isadded to the iron as a slag-forming ingredient, the improvementcomprising also adding a solid solution of a flux consisting essentiallyof 28 to 32% MnO, 30 to 35% P60, to C210 and 8 to 12% MgO.

4. The process of claim 3 wherein the solid solution flux consistsessentially of 28% MnO, FeO, 25%

1. A SOLID SOLUTION OF FLUX CONSISTING ESSENTIALLY OF 28 TO 32% MNO, 30TO 35% FEO, 25 TO 30% CAO AND 8 TO 12% MGO.
 2. A solid solution fluxencompassed by claim 1 and consisting essentially of 28% MnO, 35% FeO,25% CaO and 12% MgO.
 3. In a pneumatic process for refining iron intosteel where lime is added to the iron as a slag-forming ingredient, theimprovement comprising also adding a solid solution of a flux consistingessentially of 28 to 32% MnO, 30 to 35% FeO, 25 to 30% CaO and 8 to 12%MgO.
 4. The process of claim 3 wherein the solid solution flux consistsessentially of 28% MnO, 35% FeO, 25% CaO and 12% MgO.
 5. A solidsolution of a flux consisting essentially of approximately 80% CaO, 15%MnO and 5% FeO.
 6. In a pneumatic process for refining iron into steel,the improvement comprising adding to the iron a solid solution of a fluxconsisting essentially of 80% CaO, 15% MnO and 5% FeO.